Correlation of Small-Signal Modulation with Digital Modulation Characteristics of High-Speed Semiconductor Lasers

摘要

This paper introduces correlation of the small-signal modulation characteristics with those of digital modulation of high-speed multiple-quantum-well semiconductor laser. The accuracy of applying the common small-signal approximation to calculate the modulation bandwidth is evaluated by comparing the obtained values with those calculated by the reliable technique of time-integration of the rate equations. Also, we present correlation between the maximum bit rate and the small-signal bandwidth at given bias current and modulation index. We show that the bandwidth frequencies predicted by the small-signal approximation are higher than those calculated by the time integration. The difference increases with the increase of the bias current reaching 8 GHz when the current exceeds 3.5 times the threshold current. We predict also the modulation conditions required to achieve modulation speed as high as 40 Gbps. The ratio of the maximum bit rate to the small-signal bandwidth exceeds unity and reaches 1.6 under deep modulation with modulation index equal to 0.5.